No, they don't do that to our work PCs... I am also IT staff (I am analyst-programmer and occasionally also do a little network admin stuff) so I have more accesses than regular users... That said, we found the culprit... A network admin that left ages ago had setted up a job to "update" our PC to Firefox 29... The job was poorly written and kept trying to "update" any Firefox which was not version 29... I would update my Firefox to the latest and I would see it downgraded to version 29 when their server would try to push the "update"... I was not the only job which was trying to push older version of applications but it looks like only Firefox was happy with downgrading to version 29 from a later version...??? (the only switch that was used is -ms which I think is for a silent install...) Would it be worth it to open a ticket to ask that Firefox not be so happy to downgrade to an earlier version? Thank you and have a nice day!